Sequencing And Analysis Of The Mitochondrial Genome Of Hirsutella Rhossiliensis

Mitochondria is a major organelle responsible for energy supply in eukaryotic cells.It forms a independent genetic system during evolution,and it records the rich historical information in the process of biological evolution and is of great significance in the identification,classification,phylogeny and phylogenetic analysis of fungi.Nematode is a widely distributed plant pathogen and it could cause serious threat to agricultural production.Thus,the biocontrol of nematodes has become a hot spot of biological control research.Hirsutella rhossiliensis is a common endophytic fungus of nematodes and it could produce toxins to digest nematodes,thus effectively reduce the damage of nematodes to plants.Therefore,Hirsutella rhossiliensis becomes an important material for controlling nematodes.Although the genus of Hirsutella contains many species,only three species have published complete mitochondrial genomes.The mitochondrial genome of Hirsutella rhossiliensis USA-87-5 strain has been published,but we found that there may be errors when we use this mitochonthdrial genome sequence.Therefore,the research purpose of this paper is to(1)report correct mitochondrial genome of Hirsutella rhossiliensis and analyze its structural composition characteristics;(2)correct the previously published mitochonthdrial genome sequence of USA-87-5 strain;(3)phylogenetic analysis and compare the mitochondrial genome of Hirsutella rhossiliensis with the mitochondrial genomes of Hirsutella minnesotensis and H.vermicola.In this study,the Hirsutella rhossiliensis strain OWVT-1 was used as the research material.We screened out the mitochondrial genome fragments from the high-throughput sequencing results and assemble them together on the basis of PCR amplification and sanger sequencing results to obtain the complete mitochondrial genome sequence.The mitochondrial genome of Hirsutella rhossiliensis is a circular DNA molecule with the length of 62949 bp.It contains 14 PCGs,2 rRNA genes,26 tRNA genes and 7 free-standingORFs.13 introns are distributed in 7 genes and they encode the protein rps3,GIY-YIG or LAGLIDADG homing endonuclease.The nucleotide composition shows a characteristic of high AT content,and preferring to use A and U-terminated codons.The intergenic region is long and there are no long fragments duplication in this mitochondrial genome.The original alignment showed that there was difference of 466 bp between mitochondrial genomes of OWVT-1 and USA-87-5(KU203675),which contain three long insertion/deletions and small indels.Through PCR amplification and electrophoresis,we finally confirmed that there was no difference in two mitochondrial genomes.The mitochondrial genomes of three Hirsutella fungi had a strong collinearity and had higher conservation in gene composition,gene order and frequency of amino acid use.The length of the intergenic region is the most important factor affecting the mitochondrial genome size of the three fungi.This study enriched the mitochondrial genomic database of the genus Hirsutella.